+ ## calculate leftmost colum
+ left = if force_alignment # force mode: align exactly
+ message_left
+ else # regular: minimize cursor movement
+ ## leftmost and rightmost are boundaries of all valid left-column
+ ## alignments.
+ leftmost = [message_left, message_right - buffer.content_width + 1].min
+ rightmost = message_left
+ leftcol.clamp(leftmost, rightmost)
+ end